docs: def check_variable_names(self, ds):
          """
          Ensures all variables have a standard_name set.
          """
          msgs = []
          count = 0
  
          for k, v in ds.variables.items():
              if 'standard_name' in v.ncattrs():
                  count += 1
              else:
                  msgs.append("Variable '{}' missing standard_name attr".format(k))
  
          return Result(BaseCheck.MEDIUM, (count, len(ds.variables)), 'Variable Names', msgs)